Good HDD? Take your pick.....Maxtor, Seagate, IBM, Fujitsu (yes, you read that right
I personally have had great success with the IBM Deskstars. If you are only going to run your system for a day and turn it off at night, go for the 120GXP. They are truely wonderful for speed. If you plan on 24/7 operation, go for the 60GXP. (120GXP arn't designed for 24/7 operation, that's all) Fujitsus are a good buy too; run almost completely silent, and fast transfers too.
STAY AWAY FROM SAMSUNG HDDs. I have seen these fail all too often.
Maxtors have good return policies; that I know for sure
Seagates are good and have a decient return policy
If you are interested, just found a 40GB IBM 120GXP HDD at NEWEGG.COM for $71. Not a bad buy.
Good luck